Liquid crystal displays (LCD's) are widely used in different types of electronic equipment including portable computers and portable data terminal devices. Typically, LCD's are comprised of a glass “sandwich” comprising front and back panels with liquid crystal elements sandwiched therebetween. To provide the best performance (clarity, brightness, angular visibility, resolution etc.), additional panels made of transparent or reflective plastic films are adhered to the front and back panels. Such panels include but are not limited to image enhancement polarizers, diffusers and the like.
High brightness LCD's are often required in compact, portable equipment and a typical display unit comprises a thin planar LCD sandwich with a light-guiding backlight assembly to illuminate the LCD for information display. The backlight assembly is adapted to provide a uniform distribution of light intensity across the LCD in order to present a uniform image on the display.
The backlight assembly may include one or more cold cathode fluorescent lamps (CCFL's) or an array of light-emitting diodes (LED's) configured to directly illuminate the back surface of the LCD. Alternatively, an array of LED's may be placed at one or more edges of the LCD to provide illumination.
The quantity of LED's required to provide a high-brightness display depends upon the size of the display panel and the luminance intensity of each LED. In addition, the amount of power required to operate the display, the heat generated by the display and the manufacturing cost are additional factors affecting the manufacturing process.
LCD's are inherently sensitive to shock, vibration and pressure. Many applications, however, including government and military, often require drop testing of a display unit onto concrete from a height of three or four feet.
To meet this requirement, a front cover glass faceplate is often used to ruggedize and protect the display panel. The cover glass may be adhesively attached to the front surface of the panel using double-sided adhesive foam tape, or can be optically bonded to the panel using suitable adhesive materials, well known in the art. Bonding methods, however, tend to physically deform the LCD sandwich causing non-uniform bright or dark spots in a uniformly excited image.
It can be appreciated that a ruggedized LCD unit having high brightness, low power consumption and a non-deforming cover glass structure would be a welcome addition to the LCD family.